Kristin J. Redmond, MD, MPH
Formal discussant of the CCTG SC.24/TROG 17.06 trial, Kristin J. Redmond, MD, MPH, of The Johns Hopkins University School of Medicine, Baltimore, expressed confidence in the findings of Dr. Sahgal’s study. “We now have level 1 data to support a stereotactic body radiation therapy (SBRT) dose of 24 Gy in two fractions as the standard of care in patients with painful spinal metastases meeting study eligibility criteria.” She noted that the optimal dose fractionation schedule is still not established.
Cross-Trial Comparison
Dr. Redmond contrasted the current CCTG study with RTOG-0631,1 a separate phase II lead-in to a phase III study of patients with one to three metastatic sites on the spine comparing SBRT to external-beam radiation therapy. RTOG-0631 showed no difference between the treatment arms in patient-reported pain relief. “Many of us were surprised at those findings,” she said.
She explained that the two studies had a number of differences that could account for the different results. They included some subtle and not-so-subtle differences in study design, patient characteristics, tumor characteristics, location of treatment sites, stratification factors, extent of epidural involvement in the two trials, differences in target delineation, pain measurement metrics, and quality assurance.
Finally, the two studies had differences in the dose of SBRT. In the current study, SBRT was 24 Gy in two fractions; in RTOG-0631, SBRT was given at 16 to 18 Gy in one fraction, which is biologically a lower dose.
“The optimal dose fractionation schedule remains to be determined in future randomized trials,” Dr. Redmond said.
DISCLOSURE: Dr. Redmond has received honoraria, research funding, and travel expenses from Accuray and Elekta AB and has received reimbursement for travel expenses from AstraZeneca.She participates in a data safety monitoring board for BioMimetix.
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